The process of gas exchange is by (1) .............…When substances pass in this manner, they move from areas of (2) ................. to areas of their (3)................. Thus oxygen continually passes from the (4)................ and then from the (5)................. Conversely carbon dioxide moves from the(6)................. and from (7)................... From there it passes out of the body during expiration. As a result of such exchanges, arterial blood tends to be (8).................. while venous blood is (9) ...................